-Avoid keeping your car idle for more than one minute.-For better mileage, drive within or below the speed limit.-Don’t exert a sudden increase in speed or pump the accelerator pedal-start and stop gradually for less fuel use.-When in an open highway, roll up the windows to reduce drag.-Using the car air conditioner on a hot day can decrease mileage. -The tires should be at the suggested air pressure.-The car engine should be correctly tuned.

Thanks for the tips.There several things, first replace all your filters. Fuel, Air, Breather, etc.. Get your fuel system flushed. Make sure you're up to date on your maintenance. Such as tune-up, transmission. Next use you Cruise control if you have one.Check the best average mph for your car drive at that speed try not to break heavily.

Found interesting point about how air conditioner affects fuel consumption:

"Depending on the efficiency of the system, turning on the AC uses from 15-30 horsepower. Logic would say that we should get better fuel economy with the AC off. That is true, but only up to a certain point. n slow driving or in traffic, the car will definitely consume more fuel with the AC on. However, it has been proven that if you are traveling at interstate speeds, driving with the AC off and the windows down increases drag to the point of actually increasing your fuel consumption. A study in Europe actually documented a 7 percent increase in fuel consumption when driving at 70 mph with the windows down.

So, in this case, it would be better to turn on the AC if you are on the highway and roll the windows up. Obviously, the best situation for fuel efficiency would be driving at a steady state on the interstate with the windows up and the AC off. But that would be ridiculous unless it is winter because you would be sweating profusely in no time at all."

Driving smoothly is much more efficient. Hard accelerating and sudden braking could use up to 40 per cent more fuel according to research... The majority of cars run at their most efficient at 60mph. Every five mph above that you drive, you will lose six per cent of your fuel economy. Consider this saving when you are driving on the motorway and nearing the speed limit.

I have seen that mostly people provide some general tips for maximum fuel efficiency, but the tip provided by you are different. I would also like to suggest to use public transport system. Its will reduce the use of private vehicles and congestion on the streets.